diff --git a/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_6_0/4910-dm-migration-error-for-oracle-19c.yaml b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_6_0/4910-dm-migration-error-for-oracle-19c.yaml
new file mode 100644
index 00000000000..416486acc5e
--- /dev/null
+++ b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_6_0/4910-dm-migration-error-for-oracle-19c.yaml
@@ -0,0 +1,4 @@
+---
+type: fix
+issue: 4910
+title: "Remove some references to `all_constraints` table in oracle database migration tasks which were causing errors for version 19c."
diff --git a/hapi-fhir-sql-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/taskdef/DropIndexTask.java b/hapi-fhir-sql-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/taskdef/DropIndexTask.java
index 7b566a871b4..12fc29f8398 100644
--- a/hapi-fhir-sql-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/taskdef/DropIndexTask.java
+++ b/hapi-fhir-sql-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/taskdef/DropIndexTask.java
@@ -160,11 +160,9 @@ public class DropIndexTask extends BaseTableTask {
 			@Language("SQL") String dropConstraintSql = "ALTER TABLE " + getTableName() + " DROP CONSTRAINT ?";
 			findAndDropConstraint(findConstraintSql, dropConstraintSql);
 		} else if (getDriverType() == DriverTypeEnum.ORACLE_12C) {
-			@Language("SQL") String findConstraintSql = "SELECT DISTINCT constraint_name FROM user_cons_columns WHERE constraint_name = ? AND table_name = ?";
+			@Language("SQL") String findConstraintSql = "SELECT constraint_name FROM user_constraints WHERE constraint_name = ? AND table_name = ?";
 			@Language("SQL") String dropConstraintSql = "ALTER TABLE " + getTableName() + " DROP CONSTRAINT ?";
 			findAndDropConstraint(findConstraintSql, dropConstraintSql);
-			findConstraintSql = "SELECT DISTINCT constraint_name FROM all_constraints WHERE index_name = ? AND table_name = ?";
-			findAndDropConstraint(findConstraintSql, dropConstraintSql);
 		} else if (getDriverType() == DriverTypeEnum.MSSQL_2012) {
 			// Legacy deletion for SQL Server unique indexes
 			@Language("SQL") String findConstraintSql = "SELECT tc.CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS tc WHERE tc.CONSTRAINT_NAME = ? AND tc.TABLE_NAME = ?";
diff --git a/hapi-fhir-sql-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/taskdef/ModifyColumnTask.java b/hapi-fhir-sql-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/taskdef/ModifyColumnTask.java
index 13f268932c8..149b1b32a28 100644
--- a/hapi-fhir-sql-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/taskdef/ModifyColumnTask.java
+++ b/hapi-fhir-sql-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/taskdef/ModifyColumnTask.java
@@ -164,10 +164,10 @@ public class ModifyColumnTask extends BaseTableColumnTypeTask {
 			case ORACLE_12C:
 				@Language("SQL") String findNullableConstraintSql =
 					"SELECT acc.owner, acc.table_name, acc.column_name, search_condition_vc " +
-						"FROM all_cons_columns acc, all_constraints ac " +
-						"WHERE acc.constraint_name = ac.constraint_name " +
-						"AND acc.table_name = ac.table_name " +
-						"AND ac.constraint_type = ? " +
+						"FROM all_cons_columns acc, user_constraints uc " +
+						"WHERE acc.constraint_name = uc.constraint_name " +
+						"AND acc.table_name = uc.table_name " +
+						"AND uc.constraint_type = ? " +
 						"AND acc.table_name = ? " +
 						"AND acc.column_name = ? " +
 						"AND search_condition_vc = ? ";
@@ -176,9 +176,8 @@ public class ModifyColumnTask extends BaseTableColumnTypeTask {
 				params[1] = tableName.toUpperCase();
 				params[2] = columnName.toUpperCase();
 				params[3] = "\"" + columnName.toUpperCase() + "\" IS NOT NULL";
-				List<Map<String, Object>> queryResults = getConnectionProperties().getTxTemplate().execute(t -> {
-					return getConnectionProperties().newJdbcTemplate().query(findNullableConstraintSql, params, new ColumnMapRowMapper());
-				});
+				List<Map<String, Object>> queryResults = getConnectionProperties().getTxTemplate().execute(t ->
+					getConnectionProperties().newJdbcTemplate().query(findNullableConstraintSql, params, new ColumnMapRowMapper()));
 				// If this query returns a row then the existence of that row indicates that a NOT NULL constraint exists
 				// on this Column and we must override whatever result was previously calculated and set it to false
 				if (queryResults != null && queryResults.size() > 0 && queryResults.get(0) != null && !queryResults.get(0).isEmpty()) {